1. Field of the Invention
The present invention relates to automatic slide door operating systems in which the opening and closing movement of the door is carried out with the aid of a power device upon manipulation of a control switch. More specifically, the present invention is concerned with the automatic slide door operating systems of a type which permits manual movement of the door under failure of the automatic operating system.
2. Description of the Prior Art
Hitherto, in motor vehicle, particularly, in so-called "one-box" type motor vehicles having slide doors, various types of automatic door operating systems have been proposed and put into practical use for opening and closing the door with the aid of a power device. One of such systems is disclosed in U.S. patent application Ser. No. 07/526,653 filed on May 22, 1990 now U.S. Pat. No. 5,018,303 in the names of Soushichi KOURA et al.
The system described in the prior patent comprises a drive cable which has a part fixed to the door and has a linear part extending along the guide way for the door, a drive drum which is mounted on the vehicle body and has both ends of the drive cable wound therearound, a reversible electric motor which drives the drive drum in one or the other direction upon energization, an open-close control switch which is mounted near a driver's seat for controlling the motor and a door open detecting switch which, upon full opening of the door, breaks the electric feeding to the motor.
The system further comprises a so-called "fail-safe" means which permits manual movement of the door under failure of the automatic door operating system. Under manual movement of the door, the rotor of the electric motor then deenergized is forced to rotate by the drive cable moved with the door.
However, the system has the following drawback due to its inherent construction.
That is, under failure of the automatic door operating system, there is produced a closed circuit which includes the electric motor and the door open detecting switch. Thus, the manual movement of the door, which forces the rotor of the motor to rotate, causes the motor to generate electric power thereby producing a considerable resistance to the movement of the door. Thus, under this condition, smooth manual movement of the door is not obtained.
One of methods to eliminate the above-mentioned drawback is to open the closed circuit under failure of the automatic door operating system.
However, this method brings about the following new drawback.
That is, when, with the motor vehicle parking on a sloping road with its front portion sloped down, the slide door is moved up obliquely to the full-open position by the automatic operating system, the door open detecting switch automatically functions to break or open the closed circuit Thus, under this condition, the door tends to slide obliquely downward by its own weight because the rotation of the rotor of the electric motor does not produce any resistance to the movement of the door.